1. Field of the Invention
The present invention relates to an output control apparatus for a CO.sub.2 gas laser oscillator employed in laser machining, such as cutting, etc.
2. Description of the Background Art
FIG. 7 is a block diagram illustrating the arrangement of an output control apparatus for a laser oscillator known in the art. In FIG. 7, part of a laser output 3 provided by an output mirror 2a in a laser oscillator 1 is extracted from a rear mirror 2b in the laser oscillator 1 and is input to a power sensor 4 constituted by a thermocouple in order to determine the intensity of the laser output 3. A control circuit 5 compares and amplifies an error signal between the value of a desired intensity of the laser output, as given by a laser output command 6, and the value of the output signal (proportional to the intensity of the laser output 3) of the power sensor 4 and provides the result to a power supply device 8 as a power command 7. Under the power command 7, the power supply device 8 supplies the laser oscillator 1 with excitation power, whereby laser oscillation is performed. Namely, constant laser output control is carried out by increasing or decreasing the input power (excitation power) of the laser oscillator so that the laser output 3 detected and fed back is equal to the laser output command 6.
It is generally known in the output control apparatus for the CO.sub.2 gas laser oscillator that the power sensor for detecting the laser output is often constituted by a thermocouple, and its physical property value changes with time. In addition, it is known from experience that the change of the value with time is not linear and the property changes abruptly when it exceeds a given value.
However, the conventional output control apparatus for the laser oscillator is not equipped with a means of measuring the values or the relevant physical properties of the power sensor. Therefore, if an important property of the power sensor changes suddenly, and in an extreme case, its detection output value is zeroed during, for example, the cutting of a workpiece by the laser oscillator, the constant laser output control is disabled, causing all subsequent workpieces to be defective. Such a fault occurring during the long-time unmanned operation that often occurs at night presents a serious problem to the user of the laser oscillator.
It is an object of the present invention to overcome such disadvantages.
An object of the invention is to prevent workpieces from being defective if the property of the power sensor makes a sudden change and its detection output value changes abruptly.
An object of the invention is to output an alarm signal when the property of the power sensor has changed suddenly, thereby specifying the changing time of the power sensor.